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Alternator on a hit and miss?

Spenser Rynne

Registered
Hello, all. I've been trying to figure a way of having 120vAC power at shows to run a few old fans, an old Lionel set, etc. I've come to thinking a 10si alternator with a battery and inverter would be the best way of doing this compared to a noisy AC generator. I have an old US Falcon 5hp inboard I wanted to use, but it has no governor and I'm not so sure it would be a safe thing to run the alternator in the event of a load change, it could run away. (Or maybe it wouldn't, but I doubt it). I have an old ZD but I think it's too tired for the task. That leaves me with a '29 Dishpan 2hp FMZ. I have it running at just under rated speed, about 450 rpm. I'm thinking I could use a large pulley or maybe even the flywheel, and by my reading, I could spin the small Alt pulley at about 2500-3000rpm. My question is, how badly would the constant speed changes of the engine effect the alt? I've been thinking of using the 3 wire 10si, or an old spare Ford 1g off my pickup, so I can excite the alt without the excessive speed required by a 1 wire.
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
Personally I would find a small, old-ish AC generator, and belt drive that at around the correct speed. That way it eliminates the need for a battery and inverter, and will look more correct with the engine. Other than the speed of your fans varying a bit, the speed changes will be harmless.
 

Spenser Rynne

Registered
Personally I would find a small, old-ish AC generator, and belt drive that at around the correct speed. That way it eliminates the need for a battery and inverter, and will look more correct with the engine. Other than the speed of your fans varying a bit, the speed changes will be harmless.
From what I'm reading this will throw the 60 cycle AC all over the place, wouldn't that burn things up? Also. I've been trying to find an old belt driven AC generator for other uses without much luck. I could always use the inverter for other things as well.
 

Tracy T

Subscriber
Last Subscription Date
07/16/2019
From what I'm reading this will throw the 60 cycle AC all over the place,
it shouldnt if you are running a battery & inverter. the only thing you are generating is dc to the battery, and the delco has a its own regulator.
 

Spenser Rynne

Registered
it shouldnt if you are running a battery & inverter. the only thing you are generating is dc to the battery, and the delco has a its own regulator.
Oh I understand that. I was replying to the fellow who suggested an AC generator on the hit and miss.

Forget the 10SI go with a 12, 17 or best a 25 si
I haven't done much reading on them yet. What's different with them roughly? I'll have to read up on it when I get a minute.
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
Yes, the ac frequency would vary as the speed does, but if a simple self excited AC generator was used (all of the smaller old ones were) the voltage will also vary with the speed. So, incandescent lamps would flicker with the hits and the misses, and the fans would slow a bit and speed up a bit, but no harm would come from it.

Small fan motors are designed to operate with so much slip (operating well below synchronous speed), and have so much rotating mass (in relation to their feeble torque output) that they would end up running at a fairly constant speed anyway.

But certainly the small automotive generator (alternator), battery, and inverter would work fine as well. I'd suggest a fairly small one as they are notoriously inefficient. Your small engine may struggle to drive a large one, even with only a modest load on it. :brows:

Keith
 

turtmaster

Subscriber
Last Subscription Date
10/03/2019
You might have to use something like 10-25 feet of 10 or 12 awg wire, experiment with the length of the wire to prevent the engine from bogging down, the wire Will adding enough resistance in the line.
 

Mark Dieckmann

Registered
I just ran across this thread, I realize it is a little old. Has anyone actually tried this? It seems to me that the biggest problem might be the 2 hp. That’s not much power and given the inefficiencys in the equipment I would guess it will do more hitting than missing.
 

Odin

Subscriber
Last Subscription Date
07/13/2019
Thread isn't that old. I have actually done this.

I have a Delco 10SI alternator mounted to a bracket that clamps onto the skid of my Little Jumbo engine. A V belt is then run from the engine's flywheel to the alternator pulley. With the engine turned down to roughly 300 RPM instead of the rated 500 RPM, the alternator is spinning around 1200 RPM. My alternator is a 3-terminal alternator, and the field contact is connected through a manual switch. Like so I start the engine with the field turned off. The alternator then spins but produces no power while I start the engine and get it running properly. Then I close the switch to energize the field and make it all work.

Typically when first connected the alternator drags the engine to the ground. Sustained full loads, only misses every 2nd or 3rd charge, and if the engine stumbles it can't recover and stalls. Its rated 1 3/4 HP, I do have some blowby but it isn't in bad shape. Just the reduced power from running at 300 RPM is enough that the alternator is a full load for it at first. Once it has run a little while the alternator's output decreases and the engine can miss a few times between hits, usually by then there's steam drifting off the hopper.

I use the alternator to keep a car battery charged when I'm at shows. This battery then powers the 12v blower on my blacksmith forge, and also runs a cellphone charger for my wife so she stays happy while relaxing nearby.

At the moment I'm planning on making an updated video of the setup once the weather improves. For now here's a picture of my engine and forge all set up at a show. Its apparently too big of a picture for an inline view.

https://i.imgur.com/KJaIlBP.jpg
 

Andrew Mackey

Moderator
Last Subscription Date
05/14/2017
A friend has an IHC 11/2 HP M engine belted to a 100 amp AC Delco 1 wire alternator, off a Chevrolet. He charges a 12 volt battery and that in turn powers an inverter that runs a fan and other 110 AC items. Cool set up for an engine show. Your dish pan should also be able to do the same. He uses a modern 100 amp generater and a serpentine belt drive. Belt rides on flywheel face and the stock pulley on the generater.
 
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